1. Field of the Invention
The present invention relates to electrical busways. More specifically, the invention relates to an improved electrical busway wherein the electrical insulation between adjacent buses is maximized, and the overall space required for the busway is minimized.
2. Description of the Related Art
Electrical bus systems are commonly used to provide electricity in locations wherein the location of the final electrical load must be highly flexible. Common examples include trolley systems, light assemblies for commercial establishments, and/or electrical outlets and connections for assembly lines. Such systems typically include two to four buses (wires), with each wire being insulated on three sides and exposed on one side. A typical bus system will include four wires, with three wires providing alternating current in phases that are 120xc2x0 apart, and the fourth wire being a neutral, commonly known as a three-phase system. The housing is dimensioned and configured so that electrical loads such as light fixtures, electrical outlets, etc. may be removably secured within the housing, with contacts on the electrical load electrically connected to the buses. Typical bus systems include individual track sections, typically ranging in length from two to twenty feet, with electrical connections between the corresponding buses within each of the adjacent track sections.
Presently available bus systems use insulation around the buses having a flat back surface, and flanges or legs extending approximately 90xc2x0 away from the back surface, thereby forming approximately U-shaped channels for insulating the buses. Such a bus system must provide sufficient space between adjacent buses so that the electric potential between the two adjacent buses is insufficient to overcome the resistance of the insulating material between the buses, combined with the resistance of the air between the buses. This electrical resistance is a function of both the resistivity of the material, and the distance current must travel through the material between one bus and the adjacent bus.
Track lighting systems are similar to electrical bus systems, but are not required to provide the same level of electrical insulation. A typical track lighting system provides insulation merely through physical separation of the individual buses. One presently available track lighting system, having two buses, utilizes insulation covering three sides of each bus, with adjacent insulation sections joined together at their top ends, forming a W-shaped profile when viewed from one end.
The drawback of many presently available systems is the distance required between adjacent buses to provide sufficient electrical resistance to prevent a short between the buses. This distance requirement enlarges the overall structure of the bus section.
Some presently available bus systems also provide connectors between adjacent bus sections with the connectors providing insulation around three sides of an individual bus at the joint between adjacent track sections. Presently available connectors require removal of the insulation from around the bus bar at the joint before the connector can be used to provide insulation between adjacent track sections, thereby complicating assembly of a bus system.
Accordingly, there s a need for a bus system wherein the overall space required by the system is minimized, but the electrical resistance between adjacent buses is maximized by maximizing the distance through which electricity must travel between these buses within this minimized overall space. There is also a need for an improved connector for providing both electrical connection between corresponding buses, and insulation around the buses at the joint between adjacent track sections, thereby facilitating assembly of the bus system.
The present invention is an improved electrical bus system, wherein the distance electricity must travel from one bus to an adjacent bus, thereby creating a short, is maximized within a minimized overall space, thereby increasing the overall resistance of the insulation between adjacent buses. The present invention also provides an improved connection between adjacent bus sections, providing the necessary electrical connections and insulation, and simplified assembly. The bus system includes a plurality of bus sections, with each section having a housing, a bus bar insulator, and two to four bus bars. The individual track sections are joined by joint insulators and connectors.
Each bus section preferably includes at least two buses (wires) for carrying electricity between its source and its load. A preferred embodiment includes four buses, with three of the buses carrying alternating electrical current in phases 120xc2x0 apart, and a fourth neutral bus, commonly known as a three-phase system. The neutral bus is preferably located between two of the three live buses. Because the electric potential between a live bus and a neutral bus is approximately one-half the potential between two live buses located the same distance apart, the neutral bus may be located relatively close to the live buses on either side. Therefore, the only place within the track section requiring substantial space between adjacent buses is the one location wherein two live buses are adjacent to each other.
A bus bar insulator surrounds the buses. The bus bar insulator is made from electrically resistive material, for example, plastic. The bus bar insulator includes an upside down U-shaped section dimensioned and configured to receive each bus bar, with adjacent U-shaped sections connected at their bottom ends. The inside walls of the bus bar insulator include flanges dimensioned and configured to retain the bus bars at the top of the U-shaped sections. The resulting configuration would require electricity traveling from one bus bar to an adjacent bus bar through the insulation to travel from the top to the bottom section of the first bus insulator section, across the joint between adjacent sections, and then from the bottom to the top of the second bus insulator section. This relatively long distance between adjacent bus bars through the insulation maximizes the total resistivity through the insulation between adjacent bus bars. Because the resistivity of air is higher than the resitivity of the insulation, the individual bus bars may be located closer together horizontally without the risk of a short created by current passing through the air, and without reducing the distance through the insulator that current must travel to create a short. The bus insulation preferably terminates a short distance from the end of the buses within a given track section, with an example distance between the end of the bus bar and end of the insulation being approximately one inch.
The housing includes a middle section dimensioned and configured to contain the bus bars and bus bar insulator, a top section dimensioned and configured to secure the bus section to a ceiling, and a bottom section dimensioned and configured to receive and secure electrical devices such as lighting systems and electrical outlets.
Adjacent bus sections are joined utilizing a joint insulator and a connector. The joint insulator includes a top section and a plurality of downwardly extending legs, with each leg fitting either between two adjacent buses, or on either side of the row of buses. One end of a joint insulator fits between the bus insulator and the housing, and the other end is substantially even with the end of the housing. In use, the joint insulators bridge the gap between the bus insulators of adjacent bus sections, fitting above each bus bar insulator, between this insulator and the housing. The joint insulator covers that portion of the bus bars not covered by the bus bar insulator.
The connector includes a plurality of electrically conductive U-shaped clamp structures, with each clamp dimensioned and configured to snap onto a single bus bar within two adjacent track sections, thereby forming an electrical connection between these two bus bars. The connector therefore includes one U-shaped clamp for each pair of bus bars to be electrically connected. The remainder of the connector is made from electrically insulating plastic, thereby providing additional insulation around the joint between adjacent track sections. When a bus system is being assembled, a pair of adjacent sections will be mounted in their desired location (preferably on the ceiling), with the joint insulator fixed in each section to cover the ends of the busbars, and a connector will be snapped in place, securing the exposed ends of the buses at the joint.
An electrical load, such as a light fixture or electrical outlet, will be electrically connected to the buses by plugging into the bottom of the bus assembly. The electrical load will have a prong corresponding to each of the buses within the bus assembly. The electrical load will also include means for removably securing the load to a desired location within a track section. Preferred and suggested means include spring retention devices, having flanges dimensioned and configured to engage the bottom portion of the housing, and finger engaging portions, which, when depressed, bias the flanges away from the housing, permitting the electrical load to be removed.
It is therefore an aspect of the present invention to provide an electrical bus system wherein the distance electricity must flow between adjacent buses to create a short is maximized within a minimized overall space.
It is another aspect of the present invention to provide an electrical bus system wherein individual bus sections may be joined without the need for removing material from any portion of either section.
It is a further aspect of the present invention to provide an electrical bus system wherein adjacent sections may be joined by snapping a connector into place across the corresponding buses within the adjacent sections.
These and other aspects of the invention will become apparent through the following description and drawings.